Electric fan with oil-retaining structure

ABSTRACT

An electric fan includes a fan base ( 10 ), a bearing ( 40 ), a rotor assembly ( 20 ), and an oil-retaining structure. The fan base forms a center tube ( 11 ) receiving the bearing therein. The rotor assembly includes a fan hub ( 22 ), and a pivot axle ( 23 ) joined to the fan hub. The pivot axle pivotably extends into the bearing. The oil-retaining structure can be pivoted with the rotor assembly. The oil-retaining structure defines an oil slot ( 25 ) surrounding the pivot axle. At least one oil guide rib ( 26 ) is formed in the oil slot. As the fan is operated, the lubricant oil is thrown into the oil slot, and then thrown out of the oil slot along the oil guide rib.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to an electric fan, and more particularly to an oil-retaining structure for the electric fan to prevent a leakage of lubricant oil.

2. Description of Related Arts

As ICs (Integrated Circuits) such as computer CPUs (Central Processing Units) are being designed to run faster and faster, more and more heat are being generated by these ICs. Electric fans are typically used to dissipate the heat generated by these ICs.

One of such electric fans typically includes a stator assembly and a rotor assembly pivotable with respect to the stator assembly. A bearing is usually used to pivotably support a pivot axle of the rotor assembly. Lubricant oil is usually used to lubricant an interface of the bearing and the pivot axle, thereby reducing noise caused by physical contact during pivoting of the pivot axle, and reducing wears on the pivot axle and the bearing to extend lifetime of the fan. However, the lubricant oil is prong to lose during use of the fan. One reason, among others, is that the lubricant oil is thrown out of the bearing under a centrifugal force generated by the pivot axle as the fan is operated. As the lubricant oil loses, the performance of the fan, such as noise control, fan operation stabilization, rapidly deteriorates. Finally, the fan cannot be used once the lubricant oil is exhausted. What is desired, therefore, is to provide a structure to prevent the lubricant oil from loss.

SUMMARY OF THE INVENTION

The present invention, in one form thereof, provides an electric fan having an oil-retaining structure that can prevent a leakage of lubricant oil. According to one embodiment, the electric fan includes a fan base, a bearing, a rotor assembly, and an oil-retaining structure. The fan base forms a center tube to receive the bearing therein. The rotor assembly includes a fan hub, and a pivot axle joined to the fan hub. The pivot axle pivotably extends into the bearing. The oil-retaining structure is fixed to the rotor assembly and can rotate with the rotor assembly. The oil-retaining structure defines an oil slot surrounding the pivot axle. At least one oil guide rib is formed in the oil slot. As the fan is operated, the lubricant oil is thrown into the oil slot, and then thrown out of the oil slot along the oil guide rib.

Other systems, methods, features and advantages of the present invention will be drawn from the following detailed description of the preferred embodiments of the present invention with attached drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded, isometric view of an electric fan in accordance with a preferred embodiment of the present invention;

FIG. 2 is an isometric view of a rotor assembly of the electric fan of FIG. 1, but viewed from a different aspect;

FIG. 3 is an enlarged view of a circled portion III of FIG. 2;

FIG. 4 is an assembled, cross sectional view of the electric fan of FIG. 1;

FIG. 5 is an isometric, exploded view of an electric fan in accordance with an alternative embodiment of the present invention;

FIG. 6 is an enlarged, isometric view of an oil-retaining structure of the electric fan of FIG. 5; and

FIG. 7 is an assembled, cross sectional view of the electric fan of FIG. 5.

DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 illustrates by way of example an electric fan in accordance with a preferred embodiment of the present invention. The fan comprises a fan base 10, a rotor assembly 20, a stator assembly 30 and a bearing 40. The rotor assembly 20 is pivotable with respect to the stator assembly 30.

The fan base 10 defines a cavity therein for receiving the rotor assembly 20 and the stator assembly 30 therein. A center tube 11 is formed at a center portion of the fan base 10. Referring also to FIG. 4, the bearing 40 is engagingly received in the center tube 11. At least one oil groove 42 is defined in an outer periphery of the bearing 40. The oil groove 42 extends axially across the bearing 40 to communicate both spaces at opposite top and bottom ends of the bearing 40. The stator assembly 30 is attached around the center tube 11. A lubricant reservoir 14 is formed in the fan base 10 below the bearing 40, for reserving the lubricant oil as the fan is operated. In this preferred embodiment, the bearing 40 has a porous structure containing lubricant oil therein and is usually referred to as an oil-permeated bearing.

Referring to FIGS. 2 and 3, the rotor assembly 20 comprises a generally cup-like fan hub 22 having a top wall and a periphery wall. A plurality of fan blades 21 is formed around the periphery wall of the fan hub 22. A pivot axle 23 extends perpendicularly downwards from the top wall of the fan hub 22. The top wall integrally forms an oil-retaining structure around a joint of the pivot axle 23 and the top wall, for preventing a leakage of the lubricant oil. In this preferred embodiment, the oil-retaining structure comprises a protrusion 29 formed on the top wall in which an end of the pivot axle 23 is embedded, and a surrounding wall 24 formed around the protrusion 29. The protrusion 29 and surrounding wall 24 cooperatively form an annular oil slot 25 of the oil-retaining structure therebetween, for receiving the lubricant oil thrown by the pivot axle 23 as the fan is operated. The oil slot 25 has a wedge-shaped cross section, and its radial width increases gradually from a closed side to an open side thereof. Referring also to FIG. 4, the surrounding wall 24 extends beyond the protrusion 29 and into the center tube 11. The center tube 11 forms an annular inner recess 12 for receiving a portion of the surrounding wall 24.

A plurality of oil guide ribs 26 radially connects the protrusion 21 with the surrounding wall 14 to divide the oil slot 25 into a plurality of oil spaces 27. In this preferred embodiment, there are four oil guide ribs 26 arranged in the oil slot 25. The oil slot 25 is thus divided into four oil spaces 27. In alternative embodiments, other number of oil guide ribs 26 may be formed. Each oil guide rib 26 has a wedge-shaped configuration, and has two opposite inclined guiding surfaces 28 facing two adjacent oil spaces 27, respectively.

Referring to FIG. 4, as the rotor assembly 20 is assembled in the fan base 10, the oil-retaining structure faces directly to the top end of the bearing 40, with the surrounding wall 24 of the rotor assembly 20 extending into the center tube 11. As the fan is operated, the pivot axle 23 is pivoted in the bearing 40. Under a centrifugal force generated by the pivot axle 23, the lubricant oil contained in the bearing 40 is drawn upwardly to lubricate the pivot axle 23 and the bearing 40, and then thrown into the oil spaces 27 of the oil slot 25 of the oil-retaining structure. Arrows in FIG. 4 show the moving path of the lubricant oil. Since the rotor assembly 20 is continuously pivoting, the lubricant oil is then thrown out of the oil spaces 27 along the guiding surfaces 28 of the oil guide ribs 26. Because the surrounding wall 24 extends into the center tube 11, the lubricant oil is prevented from being thrown out to outsides of the surrounding wall 24 and the center tube 11. The lubricant oil leaving the oil spaces 27 flows back to the lubricant reservoir 14 via the oil grooves 42 of the bearing 40. The lubricant oil in the lubricant reservoir 14 is then moved upwardly along the pivot axle 23 by the centrifugal force of the pivot axle 23 to repeat the lubricating process. As such, the lubricant oil is circulated in the fan to lubricate the pivot axle 23 and the bearing 40 as the fan is operated.

In the fan according to the preferred embodiment, the surrounding wall 24 prevents the lubricant oil from being thrown to the outsides of the surrounding wall 24 and the center tube 11. Therefore, a leakage of the lubricant oil is effectively prevented. Lubricant oil loss is reduced under normal operation of the fan. The lifetime of the fan is thus extended. In addition, the inclined guide surfaces 28 of the oil guide ribs 26 in the oil slot 25 serve to guide the lubricant oil to flow out of the oil spaces 27. This can prevent an accumulation of the lubricant oil in the oil slot 25.

In the fan according to the preferred embodiment, an oil-permeated bearing 40 is used. Alternatively, an ordinary bearing containing therein no lubricant oil may be instead used. In that case, a sufficient amount of lubricant oil is stored in the lubricant reservoir 14. During operation of the fan, the lubricant oil in the lubricant reservoir 14 circulates in the fan to lubricant the pivot axle 23 and the bearing 40.

In the preferred embodiment of the fan, the fan hub 22 integrally forms the oil-retaining structure to prevent the leakage of the lubricant oil. Referring to FIGS. 5 through 7, in an alternative embodiment of the fan, a separate oil-retaining structure 300 is used to prevent the leakage of the lubricant oil.

According to the alternative embodiment, the fan comprises a fan base, a rotor assembly 220, an oil-retaining structure 300, a stator assembly and a bearing. The fan base, stator assembly and the bearing in this alternative embodiment may have the same configuration as in the previous preferred embodiment. The rotor assembly 220 comprises a fan hub 222 having a top wall. A pivot axle 223 extends from the top wall. The oil-retaining structure 300 comprises an inner wall 310 and an outer wall 320. The inner wall 310 and the outer wall 320 cooperatively form a wedge-shaped oil slot 330 therebetween. A plurality of oil guide ribs 340 connects the inner wall 310 and the outer wall 320. Each oil guide rib 340 is wedge-shaped and has two inclined guide surface 350. The separate oil-retaining structure 300 of the alternative embodiment operates in a same way as in the previous preferred embodiment. The separate oil-retaining structure 300 is mounted to the rotor assembly 220 by interferentially fitting the pivot axle 223 into a hole (not labeled) in the inner wall 310 until the oil-retaining structure 300 abuts against the top wall of the fan hub 222.

It is understood that the invention may be embodied in other forms without departing from the spirit thereof. The above-described examples and embodiments are to be considered in all respects as illustrative and not restrictive, and the invention is not to be limited to the details given above. 

1. An electric fan comprising: a fan base comprising a center tube; a bearing received in the center tube; a rotor assembly comprising a fan hub, and a pivot axle joined to the fan hub and pivotably extending into the bearing; and an oil-retaining structure for being pivoted with the rotor assembly, defining therein an oil slot surrounding the pivot axle, at least one oil guide rib being formed in the oil slot to guide lubricant oil thrown into the oil slot to flow out of the oil slot as the fan is operated.
 2. The electric fan of claim 1, wherein the at least one oil guide rib comprises an inclined guide surface along which the lubricant oil flows out of the oil slot.
 3. The electric fan of claim 1, wherein the at least one oil guide rib comprises a plurality of oil guide ribs evenly distributed in the oil slot to divide the oil slot into a plurality of oil spaces.
 4. The electric fan of claim 1, wherein the oil slot has a wedge-shaped cross section, and its radial width at a closed side thereof is smaller than its radial width at an open side thereof.
 5. The electric fan of claim 1, wherein the oil-retaining structure is integrally formed with the fan hub.
 6. The electric fan of claim 5, wherein the fan hub comprises a protrusion in which an end of the pivot axle is embedded, a surrounding wall is formed around the protrusion, and the oil slot is cooperatively formed between the surround wall and the protrusion.
 7. The electric fan of claim 6, wherein the at least one oil guide rib connects the protrusion with the surrounding wall in a radial direction of the fan hub.
 8. The electric fan of claim 6, wherein the center tube defines an annular inner recess for receiving the surrounding wall.
 9. The electric fan of claim 1, wherein the oil-retaining structure and the fan hub are separately formed.
 10. The electric fan of claim 9, wherein the oil-retaining structure comprises an inner wall and an outer wall cooperatively defining the oil slot therebetween.
 11. An oil-retaining structure for an electric fan to prevent a leakage of lubricant oil, comprising: an outer wall portion located around a pivot axle of the electric fan; an oil slot defined within the outer wall portion for receiving the lubricant oil thrown by the pivot axle as the fan is operated; and a plurality of oil guide ribs arranged in the oil slot for guiding the lubricant oil to leave the oil slot.
 12. The oil-retaining structure of claim 11, wherein the oil slot has a wedge-shaped cross section.
 13. The oil-retaining structure of claim 11, wherein each of the oil guide ribs comprises an inclined guide surface along which the lubricant oil flows out of the oil slot.
 14. The oil-retaining structure of claim 11, further comprising an inner wall portion for being attached to the pivot axle, and the oil slot is formed between the inner wall portion and the outer wall portion.
 15. An electric fan comprising: a fan base securely receiving a bearing and a stator assembly therein; a rotor assembly having a fan hub, a plurality of fan blades extending radially outwardly from the fan hub and a pivot axle extending from a top wall of the fan hub and rotatably engaging with the bearing; and an oil-retaining structure fixed to the rotor assembly, having a wedge-shaped annular slot facing downwardly toward the fan base and surrounding the pivot axle, a plurality of ribs in the oil slot thereby dividing the oil slot into a plurality of oil spaces; wherein when the electric fan is operated, lubricating oil flows through the oil spaces.
 16. The electric fan of claim 15, wherein the oil-retaining structure is integrally formed with the fan hub.
 17. The electric fan of claim 15, wherein the oil-retaining structure and the fan hub are separately formed.
 18. The electric fan of claim 16, wherein the fan base has a tube, and the bearing is received in the tube, the oil-retaining structure having an outer wall extending into the tube.
 19. The electric fan of claim 17, wherein the fan base has a tube, and the bearing is received in the tube, the oil-retaining structure having an outer wall extending into the tube. 